Oh, I've seen it, but it didn't cross my mind. However, I knew before that Array + <something> will give you a String (with the members of that array delimited

Oh, I've seen it, but it didn't cross my mind. However, I knew before that Array + <something> will give you a String (with the members of that array delimited by a comma) followed by <something> cast into a String. I don't find that wat. Also, the reason why String+Number works is because + is overridden on strings to concatenate, while - isn't. That's why you get a NaN, but you probably know that. How would you expect it to work anyway? I don't think it's that watty. The only thing that I find wat-worthy is Object + <something>, because that truly makes little sense. There might be some ambiguous logic behind it, though.